The present invention relates to an output control apparatus of an engine of a vehicle that mounts thereon an automatic transmission having a torque converter.
In a vehicle having an automatic transmission into which an engine output is inputted through a torque converter, there could occur a stall of the torque converter. That is, there occurs such stall as a rotation speed difference (a slip) between a pump at an input side and a turbine at an output side of the torque converter increases by the fact that even if the engine output is adequately produced, although the pump rotates, the turbine stops. When this stall occurs, oil (generally, ATF: Automatic Transmission Fluid) that transmits torque from the pump at the input side to the turbine at the output side receives a shearing stress and generates heat. Further, if the stall continues, the oil in the torque converter is overheated, and this leads to thermal degradation (heat deterioration) of the oil with time and a decrease in durability of a seal member etc. provided inside the torque converter due to the heat generation of the oil.
In addition, in a state in which the vehicle does not stop, although the turbine also does not stop in the torque converter, since a rotation speed of the turbine is extremely low when the vehicle is in an extremely low speed region close to a vehicle starting speed, a stall state in which the rotation speed difference between the pump and the turbine in the torque converter increases occurs, and oil temperature increases likewise.
Thus, techniques for preventing the overheat of the oil, which when the stall or the stall state (hereinafter, simply called the “stall state”) of the torque converter continuously occurs, decreases the rotation speed difference between the pump at the input side and the turbine at the output side by reducing the engine output, have been proposed.
In Japanese Patent Provisional Publication No. 6-101510 (hereinafter is referred to as “JP6-101510”), as a condition (hereinafter, called a “stall estimation condition”) by which the torque converter is estimated to be in the stall state, “a drive range is selected” and “a vehicle speed is in the extremely low speed region that is lower than or equal to a predetermined vehicle speed” and “an engine output state is in a high output state” (these are “and”-condition) are disclosed. Then, when this condition is continuously satisfied for more than or equal to a predetermined time, the engine output is controlled to be reduced.
In Japanese Patent Provisional Publication No. 2003-269206 (hereinafter is referred to as “JP2003-269206”), as same as JP6-101510, as the stall estimation condition, “the drive range is selected” and “the vehicle speed is in the extremely low speed region that is lower than or equal to a predetermined vehicle speed” and “the engine output state is in the high output state” (these are “and”-condition) are disclosed. Then, when this condition continues for more than or equal to a predetermined time, the engine output is controlled to be reduced for only a setting time. Further, in JP2003-269206, in a case where the stall state is detected again within the predetermined time after the reduction control of the engine output is cancelled, if this stall state continues for more than or equal to a second predetermined time that is set to be shorter than the predetermined time, the engine output is controlled to be reduced. With this control, even if the stall state continually (intermittently) occurs, the overheat of the oil in the torque converter can be prevented.